Forces necessary for the disruption of the cisternal segments of cranial nerves II through XII

Abstract

Manipulation of the cisternal segment of cranial nerves is often performed by the neurosurgeon. To date, attempts at quantifying the forces necessary to disrupt these nerves in situ, to our knowledge, has not been performed. The present study seeks to further elucidate the forces necessary to disrupt the cranial nerves while within the subarachnoid space. The cisternal segments of cranial nerves II through XII were exposed in six unfixed cadavers, all less than 6 hr postmortem. Forces to failure were then measured. Mean forces necessary to disrupt nerves for left sides in increasing order were found for cranial nerves IX, VII, IV, X, XII, III, VIII, XI, VI, V, and II, respectively. Mean forces for right-sided cranial nerves in increasing order were found for cranial nerves IX, VII, IV, X, XII, VIII, V, VI, XI, III, and II, respectively. Overall, cranial nerves requiring the least amount of force prior to failure included cranial nerves IV, VII, and IX. Those requiring the highest amount of force included cranial nerves II, V, VI, and XI. There was an approximately ten-fold difference between the least and greatest forces required to failure. Cranial nerve III was found to require significantly (P < 0.05) greater forces to failure for right versus left sides. To date, the neurosurgeon has had no experimentally derived data from humans for the in situ forces necessary to disrupt the cisternal segment of cranial nerves II through XII. We found that cranial nerve IX consistently took the least amount of force until its failure and cranial nerve II took the greatest. Other cranial nerves that took relatively small amount of force prior to failure included cranial nerves IV and VII. Although in vivo damage can occur prior to failure of a cranial nerve, our data may serve to provide a rough estimation for the maximal amount of tension that can be applied to a cranial nerve that is manipulated while within its cistern.

Mobilization of the Transcavernous Oculomotor Nerve During Basilar Aneurysm Surgery

“…[12][13][14] One study quantifying the forces in situ over the cranial nerves of unfixed cadaveric heads found that the minimal force causing a mechanical failure of the third nerve was between 0.22 and 0.3 N on the right side and between 0.3 and 0.61 N on the left side. 22 These values fall in lower intervals of forces compared with those encountered in our study, probably as a result of the difference in the quality of fixed and unfixed specimens. Even though it would be inaccurate to directly extrapolate the absolute calculated tension to live conditions, the aim of our cadaveric study was to elucidate the pure mechanical response of the nerve before and after its transcavernous mobilization in a geometrical setting almost identical to that of real surgery.…”

Intermittent oculomotor nerve paresis and hollow appearance on MRI manifested by pituitary adenoma

“…Afterward, it courses in the lateral wall of the cavernous sinus below the CN III [13]. Laboratory investigation showed that the mechanical forces necessary to disrupt the CN III were larger, compared to the trochlear nerve [14]. In contrast, compared to the CN III, the trochlear nerve is less frequently impaired in patients with pituitary adenomas [2], [4].…”

Delayed Pneumocephalus-Induced Cranial Neuropathy

“…The oculomotor and abducens nerves are amongst the most resilient cranial nerves, requiring considerably higher forces to result in functional impairment [5]. Several mechanisms exist by which intracranial air can develop enough disruptive strength to cause direct cranial nerve compression.…”